1. Field of the Invention
The present invention relates generally to a shielding device served to shield electronic components in wireless communication apparatuses and, more particularly, to a shielding case that is capable of mitigating interference between the electronic components that are shielded by the same shielding case.
2. Description of the Prior Art
Modern day wireless communication apparatuses such as cellular phones or GPS tracking systems are becoming more and more complex as technology develops. Consumers demand smaller devices that still maintain good reception, high overall performance and large frequency range. Component placement is crucially important at RF frequencies, as interference from various components can hinder or block reception of signals. To avoid as much as possible any unwanted influence of electromagnetic radiation from devices such as RF power amplifiers or baseband chips, it is known to shield such radiation sources by encasing the radiation sources in metallic shielding cases.
However, when the RF transceiver and the RF power amplifier, which are mounted on the same printed circuit board (PCB) in a wireless communication apparatus, are encased together by only one shielding case, a so-called power amplifier (PA) pulling effect easily occurs in direct-conversion transmitter (DCT) architecture. It is believed that the PA pulling effect is caused by the higher-order harmonics power originated from the RF power amplifier, which adversely affects the signal integrity of synthesizer within the same frequency channel. As a result, the RF transceiver and the RF power amplifier are typically covered with two independent shielding cases, respectively, in order to prevent the PA pulling effect.
There is a need in this industry to reduce the manufacturing cost by using single shielding case instead of multiple shielding cases on a PCB to encase the RF transceiver and the RF power amplifier in one enclosed space. The challenge is how to suppress the PA harmonic power.